Ireland is somewhat unique in the -zone for having a genuine debt crisis. Greece, Spain and Portugal (and soon Belgium) are experiencing currency crises (similar to the one that caused the UK to leave the ERM back in 1992). ... Ireland runs a respectable trade surplus w.r.t. the rest of the -zone

So, the logic here is that a surplus country can only get in trouble through genuine overindebtedness, whereas deficit countries first get overindebted as a result of their troubles?

I'd say Belgium is special, too. They have historically had more than 100% debt-to-GDP ratio...

Keynesianism is intellectually hard, as evidenced by the inability of many trained economists to get it - Paul Krugman

Countries can get in trouble in a variety of interesting and imaginative ways, so saying that surplus countries can only get in trouble through genuine over-indebtedness and deficit countries can never have a genuine debt problem would be wrong.

What is true is that in the present crisis it looks very much like the deficit countries are having a currency crisis (because the attacks are highly correlated with foreign debts and current accounts deficits, and only weakly correlated with sovereign debts and deficits), and it looks very much like Ireland is having a genuine debt crisis (since its banks are insolvent following a real estate bubble that was not an obvious macroeconomic necessity).